Circadian changes of T lymphocyte subsets in human peripheral blood

The circadian variations in circulating T cell subsets defined by monoclonal antibodies in eight healthy male volunteers were evaluated in whole blood using a flow cytometry. In all subjects, the number of lymphocytes showed a clear rhythmicity with high values at night and low values during the day. This circadian variation in circulating lymphocytes appeared to reflect largely a change in the number of T cells rather than B cells. The percentage of OKT3+ and OKT11+ cells showed a similar fluctuation with a peak at night and a depression during the day. It was found that the percentage of OKT4+ cells varied in parallel with that of T cells, particularly of OKT3+ cells, but the OKT8+ subset was not appreciably altered over a 24 h period. Thus, a circadian variation of T cells could be largely accounted for by a circadian change of OKT4+ cells. Plasma cortisol levels showed an expected circadian variation. It was also shown that there might be an intimate relationship between these circadian changes of T cell subsets and plasma cortisol levels.     

Morphology of human T lymphocyte clones

Six human T lymphocyte clones, characterized as to cytolytic activities and several surface markers, were investigated for possible morphologic correlates of function. Cytotoxic T lymphocyte clones and natural killer-like clones had basically similar morphology, but cytotoxic T lymphocytes tended to cluster in groups and had many more lipid bodies, whereas natural killer-like cells had fewer intercellular contacts and had more and larger electron-dense bodies. Dense bodies were also quite prominent in noncytotoxic clones. The latter were distinctive in having a minority of very large cells (10 to 16 microns) with many microvilli, scattered among the majority of 5- to 8-microns diameter cells.     

Internalization of human T lymphocyte receptors

Monoclonal antibodies specific to human T lymphocyte receptors are currently being used to define the biochemical structure of these proteins as well as of functionally distinct cell subsets. Since one of the antibodies (OKT3) recognizing the T3 (CD3) receptor mimics vital physiological processes involved in the activation of the immune system and has been successfully used as a therapeutical agent, we investigated one of the mechanisms underlying this antibody-receptor interaction. Our results show that after binding of OKT3, the complex (OKT3-T3) disappears rapidly from the cell surface. Using electron microscopy, we found that this down-regulation is due to the internalization of the complex. Parallel experiments performed on the T11 (CD2) and T4 (CD4)/AIDS retrovirus receptor indicate that the same mechanism applies for the down-regulation of those molecules. These data suggest that the T3, T11 and T4 receptors have a behavior comparable to other well characterized, hormonal and viral receptors; they provide information on the metabolization pathway of surface receptors and on the possible intracellular penetration of ligands like the HTLV-III/LAV agent in human T lymphocytes.     

人外周血T淋巴细胞自噬现象的观察

目的：观察分离培养的人外周血T淋巴细胞的自噬现象。方法：密度梯度离心法及尼龙棉柱法分离健康成年人外周血T淋巴细胞，分空白组及地塞米松（DXM）组，培养72小时后观察细胞光镜及电镜形态学、MDC荧光染色，并用流式细胞仪检测自噬细胞比例变化。结果：①通过自然培养后人外周血T淋巴细胞可出现典型自噬细胞形态学改变。②空白组及DXM组72小时自噬细胞发生率与0小时比较有显著性差异。③DXM组与空白组72小时自噬细胞发生率有显著性差异。结论：人外周血T淋巴细胞存在自噬现象，DXM可诱导人外周血T淋巴细胞自噬。     

Individual variation in the frequency of HLA class II-specific cytotoxic T lymphocyte precursors

The frequencies of HLA class II-specific cytotoxic T lymphocyte precursors (CTLp) were studied in number of unrelated individuals using a limiting dilution analysis system optimized for the detection of CD4+ CTLp. Peripheral blood mononuclear cells (PBMC) were enriched for CD4+ T cells by immunomagnetic depletion of CD8+ T cells. In some allogeneic combinations high CTLp frequencies were obtained with no significant difference between PBMC and CD4-enriched PBMC populations. In other combinations CTLp frequencies in CD4-enriched PBMC were found to be at least twentyfold lower than in the starting, unfractionated PBMC, suggesting a predominance in these pairs of CD8+ CTLp. In addition there was variation in CTLp frequencies against the same set of HLA class II gene products between individuals, and variation in CTLp frequencies against different HLA class II gene products within individuals. The HLA class II specificity of the assay system was demonstrated unequivocally with detection of CTLp against HLA-DR1 expressed on a murine L cell transfectant.     

Determining control parameters for dendritic cell-cytotoxic T lymphocyte interaction

Dendritic cells (DC) are potent immunostimulatory cells facilitating antigen transport to lymphoid tissues and providing efficient stimulation of T cells. A series of experimental studies in mice demonstrated that cytotoxic T lymphocytes (CTL) can be efficiently induced by adoptive transfer of antigen-presenting DC. However, the success of DC-based immunotherapeutic treatment of human cancer, for example, is still limited because the details of the regulation and kinetics of the DC-CTL interaction are not yet completely understood. Using a combination of experimental mouse studies, mathematical modeling, and nonlinear parameter estimation, we analyzed the population dynamics of DC-induced CTL responses. The model integrates a predator-prey-type interaction of DC and CTL with the non-linear compartmental dynamics of T cells. We found that T cell receptor avidity, the half-life of DC, and the rate of CTL-mediated DC-elimination are the major control parameters for optimal DC-induced CTL responses. For induction of high avidity CTL, the number of adoptively transferred DC was of minor importance once a minimal threshold of approximately 200 cells per spleen had been reached. Taken together, our study indicates that the availability of high avidity T cells in the recipient in combination with the optimal application regimen is of prime importance for successful DC-based immunotherapy.     

Diverse roles of integrins in human T lymphocyte biology

T lymphocytes are the primary cells responsible for maintaining the immune system. There are many intricate mechanisms involved in the regulation of T cells and the integrin family of adhesive surface proteins plays a pivotal role in the control of T lymphocyte activation and functions. Integrins are heterodimeric transmembrane proteins that are not merely adhesion molecules but also function in T cell coactivation by providing a scaffold for signaling and cytoskeletal proteins that are adept at transmitting signals from the inside of the cell to the outside ("inside-out signaling") or from the outside of the cell to the inside ("outside-in signaling"). The signaling property of integrins allows for rapid responses to changes in the microenviroment of the lymphocyte. Therefore, whether the T cell needs to adhere or detach, integrins can quickly accommodate either state of the cell. Once cells are guided to sites of infection, inflammation, or antigen presentation, integrins can also participate in the initiation, maintenance, or termination of the response. This review will focus on the aspects of integrin-mediated T cell coactivation, affinity and avidity control of integrins, signaling molecules involved with integrins, association of integrins in lipid microdomains, and negative regulation of integrins.     

Polyclonal human T lymphocyte activation results in the secondary functional activation of the human B lymphocyte.

The polyclonal T lymphocyte activators Con A and PHA were demonstrated to induce secretion of IgM and IgG as well as IgA antibodies in cultures of human peripheral blood lymphocytes. A similar response was seen in one-way mixed lymphocyte cultures and the kinetics, dose-response characteristics and optimal culture conditions are presented. The presence of functional T lymphocytes is a prerequisite for in vitro B lymphocyte activation in response to T lymphocyte mitogens. A narrow dose-response profile is a characteristic for both Con A and PHA and polyclonal B cell activation occurred at what have been previously regarded as suboptimal concentrations of these agents. The use of higher doses of these activators failed to generate immunoglobulin-secreting cells despite the presence of early and optimal levels of DNA synthesis in the cultures.     

Age-dependent changes of human blood lymphocyte subpopulations.

T- and B-lymphocyte populations were enumerated at four stages of life: at the newly born, infant, adult and aged stages. The proportion of T cells detected by E rosettes and an anti-human T-lymphocyte antigen (HTLA) serum incresed from new-born children to adults, then decreased with ageing. The antiserum detected less mature T cells in aged people. The percentages of cell forming 'active' E rosettes increased with ageing. Lower numbers of B cells bearing surface immunoglobulins were found in adults.Complement receptor-bearing lymphocytes (percentages and absolute numbers) decreased from new-born children to aged humans. Finally, the number of monocytes were significantly greater in the young than in adult and aged people. Such results bring new data concerning the age-dependent changes of lymphocyte subpopulations and concerning the significance of various techniques used together to detect mononuclear cell populations in the human peripheral blood.     

人T细胞亚群的微量全血染色法

本研究建立了人T细胞亚群的微量全血染色法,观察了红细胞溶解液、血细胞与OKT McAb共育时间、洗液及OKT McAb用量等因素对染色率的影响。本法只需0.4ml全血即可得到CD_3、CD_4、CD_8亚群的百分率,同时避免了传统的Ficoll分离法用血量多、淋巴细胞部分选择性丢失等缺点。     

Analysis of human T lymphocyte activation in a T cell tumor model system

The human T leukemia line Jurkat maintains functional characteristics of normal T cells in responding to inducing stimuli by the release of interleukin 2 (IL 2). Presence of a phorbol ester during stimulation eliminated the requirement for specialized accessory cells in the response to cell mitogenic agents such as the lectin concanavalin A or treatment with neuraminidase and galactose oxidase. Antibodies directed against the T cell receptor-associated antigen T3 served as efficient stimuli, especially if aided by agents that cross-link immunoglobulin, indicating that a triggering signal is received by a T cell via aggregation of its antigen receptor complex. A Burkitt lymphoma cell line, Raji, was found to selectively trigger Jurkat cells, suggesting the ability of those cells to respond to certain foreign stimuli. The Jurkat cell line has been instrumental in the purification of IL 2 and cloning of the corresponding gene. Our data suggest it can also serve as a useful model for induction of T cell responses.     

Mitogen-induced membrane changes and cell proliferation in T lymphocyte subpopulations.

Rabbit thymus-dependent lymphocytes were exposed to phytohemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM) or anti-immunoglobulin at various stages of maturation. Proliferation (induction of DNA synthesis) and early membrane events (turnover of membrane phospholipids) were measured in neonatal thymocytes, normal adult thymocytes, prednisolone-resistant thymocytes and lymph node lymphocytes. In immature thymocytes PHA induced only a marginal increase in DNA synthesis. The mitotic response increased with maturation, but only peripheral T lymphocytes exhibited maximum stimulation. Con A and PWM were able to induce DNA synthesis in immature thymocytes and the degree of stimulation was shown to increase with maturation. In contrast to the different degree of proliferation of thymocytes induced by PHA or Con A the incorporation of [14C]oleate, [14C]choline or [14C]acetate into phospholipids was stimulated to the same degree by these lectins. Reactivity of T lymphocytes, as measured by early membrane changes at different stages of maturation, to different T cell mitogens appears to be identical. Differences in degree of cell proliferation therefore may be secondary phenomena due, in part, to tissue culture conditions. Reactivity to mitogens as measured by phospholipid turnover appears to be an early acquired function in the maturation of lymphocytes of the T cell line.     

Diminished T cell surveillance function in old mice infected with lymphocyte choriomeningitis virus.

The cell-mediated immune response resulting from infection with lymphocytic choriomeningitis virus (LCMV) was compared in old (18--20 month) and young (4--6 month) random-bred ICR mice. Three separate assay systems were used: the level of virus-specific cytotoxic T-cell activity measured in vitro, time of onset of fatal cell-mediated immunopathology in vivo and adoptive transfer of inflammatory process to immunosuppressed, virus-infected recipients. The capacity of old mice to generate virus-immune effector T cells was, by all of these criteria, greatly diminished. It is suggested that the LCMV-specific T-cell response may prove a useful standard system for determining integrity of immunological surveillance function.     

Effects of human alpha-foetoprotein on human B and T lymphocyte proliferation in vitro

Purified human alpha-foetoprotein (AFP) isolated from extracts of foetal and hepatoma tissues, and from cord serum was evaluated as to its suppressive effects on in vitro lymphocyte responses to stimuli which selectively trigger human B or T cells. The effects of equivalent concentrations of individual AFP preparations were compared on lymphocyte cultures stimulated with the human B cell mitogen Staphylococcus aureus strain Cowan I organisms, with the T cell mitogen phytohaemagglutinin (PHA), and with irradiated allogeneic lymphocytes in the one-way mixed lymphocyte reaction (MLR). PHA responses were significantly inhibited by most purified preparations of AFP in a dose-dependent manner, within the concentration range of 300 to 18 μg/ml. However, individual foetal-derived AFP preparations did vary in suppressive potency on PHA responses, and attempts to reactivate an inactive AFP were unsuccessful. In parallel cultures the mitogenic response to protein A expressing Staph. aureus bacteria was normal or even slightly enhanced by AFP. The one-way MLR was effectively suppressed at higher concentrations of AFP (300–600 μg/ml) than were required for inhibition of PHA responses. The inhibitory effect of AFP on PHA-induced lymphocyte proliferation was not altered by increases in the mitogen dose. No evidence was found that AFP merely inhibits PHA responses by direct interference with mitogen or by competition for cell surface receptors with the mitogen. The results reported here indicate that human AFP effectively suppresses certain T cell-mediated reactions, but not B cell responses in vitro, and these are in line with previously reported findings in the murine AFP system.     

Cardiovascular changes during peanut-induced allergic reactions in human subjects

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Inhibition of human T lymphocyte colony formation by methylprednisolone

Methylprednisolone, at very low concentrations, inhibits colony formation by PHA-stimulated human blood lymphocytes in vitro. The inhibition is exerted at an early stage in transformation. It results not from direct effects on colony-forming cells but from inhibition of production of a soluble factor produced by accessory cells.     

脐带血的T淋巴细胞集落培养

本文应用细胞培养和免疫间接荧光法测定脐血，正常人体外周血和成人骨髓的Ｔ淋巴细胞集落形成情况及培养前后淋巴细胞亚群的变化，结果表明：脐血的ＣＦｕ－ＴＬ显著低于正常人外周血（Ｐ〈０．０１），略低于成人骨髓（Ｐ〉０．０５）培养脐血的ＣＤ３，ＣＤ４细胞含量均显著低于正常人外周血（Ｐ〈０．０１），与成人骨髓相近似（Ｐ〉０．０５）脐血的ＣＤ８细胞含量与正常人外周血和成人骨髓相似（Ｐ〉０．０５）；培养后的ＣＦｕ